Biology Topic
Diffusion
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Study focus - 3 things
- Diffusion is the movement of particles from high concentration to low concentration
- Diffusion does not need energy from the cell
- It helps gases and dissolved substances move in and out of cells
Section 1What diffusion is
Diffusion is the spreading out of particles from an area where they are crowded to an area where they are less crowded. It happens because particles are always moving. The movement continues until the particles are evenly spread.
Section 2Diffusion in living things
Cells use diffusion to move small substances across the cell membrane. Oxygen diffuses into cells for respiration. Carbon dioxide diffuses out of cells as a waste product.
Section 3Everyday examples
If someone sprays perfume in a classroom, the smell spreads through the air by diffusion. In the body, oxygen moves from the air sacs in the lungs into the blood because oxygen concentration is higher in the air sacs.
Section 4What affects diffusion speed
Diffusion is faster when the concentration difference is bigger, the temperature is higher, and the distance is shorter. Thin surfaces, like air sacs in the lungs, help substances diffuse quickly.
Examples
Oxygen concentration is higher in the lungs than in the blood. What happens next?
Oxygen diffuses from the lungs into the blood, moving from high concentration to low concentration.
A bottle of perfume is opened at the front of a classroom and students at the back smell it later. What process explains this?
Diffusion. Perfume particles spread from a high concentration near the bottle to lower concentration across the room.
Now let's water it
Session runs notes to flashcards to quiz back-to-back.